Use high precision vertex attributes.

src/gpu/GrDefaultGeoProcFactory.cpp

Index: src/gpu/GrDefaultGeoProcFactory.cpp
diff --git a/src/gpu/GrDefaultGeoProcFactory.cpp b/src/gpu/GrDefaultGeoProcFactory.cpp
index 5534888f2c3cf4a9348fc48202ba0a50d58e8753..6e2ea060dfa8606b89d8202f591408c9c0015a17 100644
--- a/src/gpu/GrDefaultGeoProcFactory.cpp
+++ b/src/gpu/GrDefaultGeoProcFactory.cpp
@@ -193,7 +193,8 @@ private:
         bool hasColor = SkToBool(gpTypeFlags & GrDefaultGeoProcFactory::kColor_GPType);
         bool hasLocalCoord = SkToBool(gpTypeFlags & GrDefaultGeoProcFactory::kLocalCoord_GPType);
         bool hasCoverage = SkToBool(gpTypeFlags & GrDefaultGeoProcFactory::kCoverage_GPType);
-        fInPosition = &this->addVertexAttrib(Attribute("inPosition", kVec2f_GrVertexAttribType));
+        fInPosition = &this->addVertexAttrib(Attribute("inPosition", kVec2f_GrVertexAttribType,
+                                                       kHigh_GrSLPrecision));
         if (hasColor) {
             fInColor = &this->addVertexAttrib(Attribute("inColor", kVec4ub_GrVertexAttribType));
         }